Alexander Graf wrote: > > On 17.05.2010, at 18:26, Anthony Liguori wrote: > > > On 05/17/2010 11:23 AM, Paul Brook wrote: > >>>> I don't see a difference between the results. Apparently the barrier > >>>> option doesn't change a thing. > >>>> > >>> Ok. I don't like it, but I can see how it's compelling. I'd like to > >>> see the documentation improved though. I also think a warning printed > >>> on stdio about the safety of the option would be appropriate. > >>> > >> I disagree with this last bit. > >> > >> Errors should be issued if the user did something wrong. > >> Warnings should be issued if qemu did (or will soon do) something other > >> than > >> what the user requested, or otherwise made questionable decisions on the > >> user's behalf. > >> > >> In this case we're doing exactly what the user requested. The only > >> plausible > >> failure case is where a user is blindly trying options that they clearly > >> don't > >> understand or read the documentation for. I have zero sympathy for > >> complaints > >> like "Someone on the Internet told me to use --breakme, and broke thinks". > >> > > > > I see it as the equivalent to the Taint bit in Linux. I want to make it > > clear to users up front that if you use this option, and you have data loss > > issues, don't complain. > > > > Just putting something in qemu-doc.texi is not enough IMHO. Few people > > actually read it. > > But that's why it's no default and also called "volatile". If you prefer, we > can call it cache=destroys_your_image.
With that semantic, a future iteration of cache=volatile could even avoid writing to the backing file at all, if that's yet faster. I wonder if that would be faster. Anyone fancy doing a hack with the whole guest image as a big malloc inside qemu? I don't have enough RAM :-) -- Jamie
